Light-sensitive silver-halide emulsions and process of manufacturing the same



Patenteday, 7

OTTO MATTHIES AND BRUNO WENIDT, OF DESSAU IN ANHALT, GERMANY, ASSIGNORSno .AGF'A AN$CO conronerron, or BINGEAMTON,.NEW YORK, A cosronnrronNE'WYORK r v LIGHT-SENSITIVE SILVEKHALIDE Eo'DrawingQ Application filedJanuary 28,1929, Serial No. 335,732, andin Germany January 31, 1928.

The present invention relates to photographic silver salt emulsions ofincreased stabilityylittle tendency to fog and determined grain size, tolayers containing the same and to a process for manufacturing the same.

I In our copending up lication Ser. No. 335,733,",filed this same ay wehavestated that compoundswith three or more nitrogen compounds iii-"themolecule one ofwvhich is linked to hydrogen being liable to substitutionby silver and forming of no highersolubility :t on silver chloride aregood stabilizers for photographic cmula sions.

lVe found that also sulphur compounds forming stable'silver salts withthe group --SAg, these sil-ver salts having the solubilitycharacteristics cited above, can be em- I ployed for the same purposeincmulsion manufacture. They may be added to the finished I emulsionorto its constituents at any stage 7 of their manufacture or ofemulsion-making. The compounds which form silver salts of the leastsolubilityexert the strongest effect on 95 the stability of emulsions.

W'e further found that the said compounds when present during theaddition ofthe silver nitrate solutionrestrain the growing of silverbromide grains and thus give to the emulsion asteeper gradation whileatj'the same time increasing its stability.

' By our present'process we may thus obtain emulsions of varyingsteepness jof gradation though starting with the same proportions ofconstituents. I

I The following examples illustrate the in vention: J

' Example L-A highly sensitive negative emulsion is made according toany known prescription and before the silver solution is run into thepotassium bromide solution there are added to the latter 100 milligramsof thioglycollic acid per each 100 grams of silvernitrate. There is thusobtained a very finely grained, hard emulsion, whichis particularlysuitable for copying black and white work.

Ewampi'e f2.--The procedure is the same as that described in Example 1,using as the added substance milligrams of thiolactic acid. There isobtained an emulsion which nmonsrons AND Tan erine stable silver saltsent of the emulsion BEGCESS 0F WUFAGTURING Example 3.-+;'io a negativeemulsion made with a gelatine'which produces fog according to any knownprescription, there are added per kilo of emulsion, before the pouringoperation? milligrams of QB-dimercapto-d-keto-i-lo-diphenylpenthiophen.There is obtained an improvement in durability amountlngto 50 per cent.

Emample 4 .There are added to a positive bility, in Which'there is addedto the emulsion a, sulphur compound forming a stable silver salt withthe group SAg and having no higher solubility than silver chloride.

' 2. A process of manufacturing light sensitive silver halide emulsionsof increased stability, in which there is added to a constituent of theemulsion at any stage of the manufacture a sulphur compound forming astable silver salt with the group SAg and having no higher solubilitythan silver chloride;

3. A process of manufacturing light sensi tive silver halide emulsionsof increased stability and restrained size of silver halide grains, inwhich there is added to a constitu- IlOI t'O the addition of silvernitrate a sulp iur compound forming a stable silver salt with the group--S Ag and having no higher solubilitylhen silver chloride.

4. A process of manufacturing light sensitive silver halide emulsionscomprising the step of adding allyla'rninothiobiuzolesulfhy-' d1-ate.

5. A process ofmanufacturinglight sensitive silver halide emulsionscomprising the step of adding alllylaniinothiobiazolesulfhydrate to aconstituent of the emulsion at any stage of its manufacture.

6. Light sensitive silver halide emulsions containing a sulphur compoundforming a i is suitable as a cinema film positive-e1nulsion.

stable sil ver salt with the group --SAg and heaving no highersolubility than silver chlom e.

7..Li ht sensitive silver halide emulsions cuntainmga11ylavminqthiobiazolegulfhydrate; Q In testimony WIZQRQQQ l' fgfi x-Q1111 signa-V tures. V

OTTO MATTHIES.

BRUNO WEND T'. Y

